Abstract |
The loss of pyrimidine dimers in nondividing populations of an excision-repair deficient xeroderma pigmentosum group A strain (XP12BE) was measured throughout long periods (up to 5 months) following exposure to low doses of ultraviolet light (UV, 254 nm) using a UV endonuclease-alkaline sedimentation assay. Excision of about 90% of the dimers induced by 1 J/m2 occurred during the first 50 days. The rate curve has some similarities with that of normal excision-repair proficient cultures that may not be coincidental. Rate curves for both XP12BE and normal cultures are characterized by a fast and slow component, with both rate constants for the XP12BE cultures (0.15 day-1 and 0.025 day-1) a factor of 10 smaller than those observed for the respective components of normal cell cultures. The slow components for both XP12BE and normal cultures extrapolate to about 30% of the initial number of dimers. No further excision was detected throughout an additional 90-day period even though the cultures were capable of excision-repair of other newly-introduced pyrimidine dimers. We conclude that nondividing XP12BE cells in addition to having a slower repair rate, cannot repair some of the UV-induced DNA damage. The repair in XP12BE is shown to have biological significance as detected by a cell-survival assay and dose-fractionation techniques. Nondividing XP12BE cells are more resistant to UV when irradiated chronically than when irradiated acutely with the same total dose.
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Authors | D R Hull, G J Kantor |
Journal | Mutation research
(Mutat Res)
Vol. 112
Issue 3
Pg. 169-79
(Jun 1983)
ISSN: 0027-5107 [Print] Netherlands |
PMID | 6306455
(Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- DNA, Neoplasm
- DNA Restriction Enzymes
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Topics |
- Cell Survival
(radiation effects)
- Cells, Cultured
- DNA Repair
(radiation effects)
- DNA Restriction Enzymes
(metabolism)
- DNA, Neoplasm
(metabolism)
- Fibroblasts
(metabolism)
- Humans
- Ultraviolet Rays
- Xeroderma Pigmentosum
(genetics)
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